1. Technical Field
This application relates to signal handling circuits such as radio frequency (RF) combiners and/or splitters, and more particularly to such circuits operating with multiple low impedance signal sources such as power amplifiers, filters, and other RF circuits.
2. Background Information
There is an ever increasing demand for smaller and smaller electronic devices with improved performance and additional features. Smart phones, tablets, laptop computers, and devices are now invariably expected to communicate using may different types of wireless networks such as 3G, 4G, Long Term Evolution (LTE) and other cellular, Wireless Fidelity (Wi-Fi), Near Field Communication (NFC), Global Positioning System (GPS), Bluetooth and still other protocols. Numerous analog and mixed signal design challenges exist as a result of the need to accommodate the resulting ranges of operating frequencies and wide bandwidths. In addition, a “thin is in” requirement continues to reduce the space available for antennas and other radio frequency components needed to provide this connectivity.
Deep Sub-Micron and other Complimentary Metal Oxide Semiconductor (DSM-CMOS) Integrated Circuit (IC) technologies are increasingly used to implement the mixed-signal front-ends needed in these systems. As some examples, U.S. Patent Publication 2011/0051782 by Gupta, et al., entitled “Method, System and Apparatus for Wideband Signal Processing” discusses tunable state variable filters implemented in CMOS that can be used as RF components. U.S. Pat. No. 8,483,626 by Gupta entitled “Software Defined Radio” describes a CMOS programmable front end circuit including a frequency synthesizer, up and down converter, and anti-aliasing filters, that can be programmed to adapt to different wireless technologies. Patent Cooperation Treaty (PCT) Publication 2013/138457 A1 by Gupta describes still further refinements of software-defined radio front ends including power amplifiers and an antenna matching network. Each of these patents and patent applications are assigned to the Newlans, Inc., and are hereby incorporated by reference in their entirety.
These CMOS-based solutions can operate over broad bandwidths and provide the required high density circuit integration. While this provides the dual advantage of high-frequency operation and reduced circuit area, the ability to handle the need for higher power is compromised, as a result of the lower voltage levels at which CMOS circuits operate.
Recent advancements in semiconductor technology have made power amplifiers implemented with gallium nitride (GaN) and/or gallium arsenide (GaAs) attractive for certain high-voltage, high-power applications. However integration of this type of amplifier is also not necessarily easy in every instance. They are not inherently wideband, and thus the required matching networks become complex.
Thus, although mixed signal front-ends remain at least one area where technologies such as GaAs and GaN might present an attractive solution, they too are not ideal. It would be preferable to use other more widely available technologies such as CMOS that integrate more easily with digital circuits. However, because CMOS-based amplifiers and other components typically operate at relatively lower voltage, they are not inherently able to handle as much power as corresponding GaAs or GaN amplifiers.